Smoke pots containing smoke charges based on hexachloroethane, zinc oxide and metal powder are used for a variety of different types of ammunition. In general, the smoke pots are not very highly compressed. However, certain types of ammunition which have recently appeared are exposed to such high accelerations on firing that conventional smoke pots of this type cannot be used, because tests have shown that the housings of the smoke pots are deformed by the high acceleration on firing to such an extent that the smoke pots can no longer be ejected from the shell casing. This is understandable when it is considered that, for an acceleration on firing of, for example, 18,000 g, considerable forces act on the housing of the smoke pots and particularly on the housing of the lowermost smoke pot. In addition, however, it has been found that the reaction time of smoke pots such as these is no longer reproducible either. This is explained by the fact that the reaction velocity is dependent upon the compression of the smoke charge and uncontrollable compression effects occur at the acceleration levels referred to above.
Accordingly, the object of the present invention is to provide a smoke shell filling and a process for its production, which is able to withstand extremely high accelerations on firing, for example of the order of 18,000 g, and which is comparable with conventional smoke shells for comparatively low accelerations on firing in regard to its smoke effect, stability in storage and manufacturing costs, but superior in regard to its reaction time.
According to the invention, this object is achieved by virtue of the fact that the smoke pots lie one on top of the other in complete surface contact, by virtue of the fact that the components of each pot housing consist of the same material, the load-bearing components being equal in strength, and by virtue of the fact that the smoke changes completely fill the housing and are self-supporting in themselves. In this way, an uninterrupted structure is obtained both for the stack of pots as a whole and for the individual smoke pots, the self-supporting smoke charges making a considerable contribution towards stability.
Shell fillings of the type in question normally consist of smoke pots of which the housings consist of two coaxial tubes which between them form an annular chamber for the smoke charge, the annular chamber being covered on both sides by annular covers. According to the present invention, the smoke pot housings are preferably designed in such a way that, at both ends, the outer tube comprises a projecting annular rim of reduced wall thickness, the annular rim is set back in relation to the annular chamber to form an annular shoulder in alignment with the end face of the inner tube and is formed with a screwthread on that surface which faces the annular chamber, and the annular covers are provided on their outer edge with a screwthread corresponding to the screwthread on the annular rim of the outer tube and are screwed into the outer tube with such countersinking that the surfaces of the covers are flush with the end faces of the annular rims and the inner surfaces of the covers rest, on the one hand, on the annular shoulders of the outer tube and, on the other hand, on the end faces of the inner tube. In order to show self-supporting properties, the smoke charge which completely fills the annular chamber is highly compressed, preferably under a pressure of 1300 kp/cm.sup.2.
The production of the smoke pots according to the invention with a highly compressed and, hence, self-supporting smoke charge has revealed a problem which was not previously known in smoke charges of the same composition, namely that the highly compressed smoke charges show low stability in storage which, in the extreme case, can result in complete failure of the ammunition. According to the invention, these difficulties are obviated by a process for producing the smoke pots with highly compressed smoke charges, wherein the zinc oxide is calcined at at least 900.degree. C. before being mixed with the other components of the smoke charge. For reasons which will be explained hereinafter, this treatment makes the smoke charges extremely stable in storage, in other words their stability in storage is at least equivalent to that of non-compressed or lightly compressed smoke charges.